• Later surnamed Rosa di Tivoli.
• Was a German Baroque painter.
• He was born in Sankt Goar.
• Learned to paint from his father, the landscape painter Johann Heinrich Roos.
• He was the brother of the painter Johann Melchior Roos.
• He was called to paint for Charles I, Landgrave of Hesse-Kassel, who liked him so much he gave him a sum of money to travel to Rome with, which he did in 1677.
• In Rome, he worked often in the studio of Giacinto Brandi.
• By 1681 had fallen in love with his daughter.
• In 1683, he joined a papal guild of painters, the Congregation of Virtuiosi al Pantheon.
• In 1684, he acquired a large house on Vicolo del Riserraglio in the Rione San Paolo in Tivoli, near Rome, whence his surname.
• In Tivoli, they kept a menagerie of various animals so Roos could draw from live poses.
• This house was called the "Noah's Ark" by their friends.
• In 1691, he moved back to Rome.
• He joined the Bentvueghels painters in the Schildersbent. • He had the nickname "Mercurius" because of the rapidity with which he painted; Mercury was the speedy messenger of Zeus.
• He earned money making small paintings and sketches for tourists.
• He died in poverty.